Mobile stations in wireless communications systems are generally powered by batteries. For this reason, manufacturers strive to reduce power consumption of mobile stations to enable the devices to be used for longer periods without replacing or recharging the batteries, for example by including idle modes, sleep modes, and the like.
In idle mode, a mobile station disconnects from a specific base station, but listens to periodic paging messages during paging listening intervals. The paging messages are broadcast by base stations in order to notify mobile stations of the arrival of downlink traffic and the like.
In sleep mode, a mobile station maintains a connection with a base station, but powers off except for periodic wakeup intervals. During each wakeup interval, a mobile station may decode broadcast messages, receive downlink packets, transmit uplink packets, measure base station signals, and the like.
In some wireless communications systems, such as WiMAX systems, the idle and sleep modes cannot be active at the same time. However, other wireless communications systems, such as 3GPP LTE, permit a mobile station to operate in both modes at the same time.